1. Field of the Invention
The invention relates to a controlling device for the transmission ratio of an infinitely variable transmission of a motor vehicle, whereby the transmission ratio is adjustable dependent on the position of a hydraulic control valve, which is movable under the influence of the difference between a desired and an actual engine speed.
2. Description of the Prior Art
A controlling device of this kind is disclosed in the Dutch patent 168038. Here the infinitely variable transmission consists of a pair of cone-faced pulleys between which a V-belt is tensioned and whereby each of the pulleys is adjustable in order to make it possible to adjust the transmission ratio. With the known control the transmission ratio and the engine speed as well as the input speed are always regulated such that the engine speed is adapted to the power required. The engine speed is hereby set by means of an accelerator pedal (throttle) between two limits for the operating speed of the engine in question. However, abrupt changes in the transmission ratio occur when the minimum engine speed and the maximum engine speed are reached. A solution for the latter abrupt change is offered in the above-mentioned publication. A solution for the former abrupt change is offered by the present invention. This invention is characterized in that there are also means present for regulating the minimum possible engine speed in dependence of the transmission ratio.